[PATCH V3 1/4] dt-bindings: phy: tegra-xusb: Add support for Tegra264

[Wayne Chang <waynec@nvidia.com>]

Add the compatible string for the Tegra264 XUSB PHY.

A dedicated compatible string is used instead of falling back to
nvidia,tegra234-xusb-padctl, because Tegra264 is not
programming-compatible with Tegra234, even though they share the same
DT property set. The driver selects per-SoC data from the compatible
string, and Tegra264 differs from Tegra234 in at least:

- Tegra264 uses hardware tracking mode (trk_hw_mode), while Tegra234
  disables it.
- On Tegra234, CYA_TRK_CODE_UPDATE_ON_IDLE needs to be cleared so that
  the calibration values can be captured while the controller is
  still in reset. Tegra264 does not require this, and the
  corresponding handling is not even present for it.

A fallback of nvidia,tegra234-xusb-padctl would let an OS that only
knows about Tegra234 probe Tegra264 with the wrong programming
sequence. This is also why Tegra234 did not fall back to
nvidia,tegra194-xusb-padctl in this same binding: the DT schema is
shared, but each generation needs its own compatible.

Signed-off-by: Wayne Chang <waynec@nvidia.com>
---
V2 -> V3: Add rationale to the commit message for why Tegra264 does
not use a fallback compatible, per Krzysztof's and Conor's review.
V1 -> V2: No change
 .../devicetree/bindings/phy/nvidia,tegra194-xusb-padctl.yaml     | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/phy/nvidia,tegra194-xusb-padctl.yaml b/Documentation/devicetree/bindings/phy/nvidia,tegra194-xusb-padctl.yaml
index d8de900a4fce..f6fe3c90b5b0 100644
--- a/Documentation/devicetree/bindings/phy/nvidia,tegra194-xusb-padctl.yaml
+++ b/Documentation/devicetree/bindings/phy/nvidia,tegra194-xusb-padctl.yaml
@@ -45,6 +45,7 @@ properties:
     enum:
       - nvidia,tegra194-xusb-padctl
       - nvidia,tegra234-xusb-padctl
+      - nvidia,tegra264-xusb-padctl
 
   reg:
     items:
-- 
2.25.1